﻿using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
//引入命名空间
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.IO;

public partial class ValidateCode : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        string VaCode = GenerateValidateCode();
        //Session["vc"] = VaCode;
        CreateVolidateCodeImage(VaCode );
    }
  #region 生成随机字符串
    private string GenerateValidateCode()
    { 
        int number;
        char code;
        string ValidateCode = string.Empty;
        Random random = new Random();
        for(int i=0;i<4;i++)
        {
            number =random.Next();
            if(number%2==0)
                code =(char)('0'+(char)(number%10));  
            else 
               code =(char)('A'+(char)(number%26));
           ValidateCode += code.ToString();
        }
        Session["vc"]=ValidateCode;
        return ValidateCode;
    }
     #endregion
 #region 将字符串会制成图片并显示出来
    private void CreateVolidateCodeImage(string ValidateCode)
    {
        if (ValidateCode == null || ValidateCode.Trim() == string.Empty)
            return;
        
        Bitmap image = new Bitmap((int)Math.Ceiling((ValidateCode.Length * 12.5)), 22);
       
        Graphics g = Graphics.FromImage(image);
        try
        {
          
            Random random = new Random();
      
            g.Clear(Color.White);
           
            for (int i = 0; i < 2; i++)
            {
                int x1 = random.Next(image.Width);
                int x2 = random.Next(image.Width);
                int y1 = random.Next(image.Height);
                int y2 = random.Next(image.Height);
                g.DrawLine(new Pen(Color.Black), x1, y1, x2, y2);
            }
            Font font = new Font("Arial", 12, FontStyle.Bold);
            LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
            g.DrawString(ValidateCode, font, brush, 2, 2);
           
            for (int i = 0; i < 100; i++)
            {
                int x = random.Next(image.Width);
                int y = random.Next(image.Height);
                image.SetPixel(x, y, Color.FromArgb(random.Next()));
            }
           
            g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
            MemoryStream ms = new MemoryStream();
            image.Save(ms, ImageFormat.Gif);
            Response.ClearContent(); 
            Response.ContentType = "image/Gif";
            Response.BinaryWrite(ms.ToArray());
        }
        finally
        {
            g.Dispose();
            image.Dispose();
        }
    }
#endregion
}
